To fix extreme crops when using the warp stabilizer effect.
First try the settings
Click on the advanced settings, and choose the following settings:
Reduce either the smoothness OR
Crop Less and Smooth more which is a better option to try first since it does not require a restabilization phase.
(on a side note)
If you are getting a wobbly effect then that is down to the rolling shutter effect of the camera and to fix that you would need to set Advanced > Rolling Shutter Ripple to Enhanced Reduction.
For extreme crops:
Another way I resolve those issues is to 'razor tool' around the area where the biggest 'shakes' occur causing the warp stabilizer to crop drastically.
I then redo the warp stabilizer effect for those two side clips separately, leaving the middle one untouched.
I can now choose to remove the middle clip or employ a different transition effect.